The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed.
For example, as the critical dimension (CD) of a feature is scaled down, overlay errors become problematic when performing a fin cut process while fabricating a fin field effect transistor (FinFET) device. For example, a spacer technique can be used for doubling the exposed pattern. That is, the pitch of a final pattern is reduced to only half compared with the first exposed pattern. A typical spacer technique uses two masks. The first one defines a mandrel pattern in a first exposure and the second one defines a cut pattern in a second exposure. The cut pattern removes unwanted portions of the mandrel pattern, a derivative, or both. The final pattern includes the mandrel pattern plus the derivative but not the cut pattern. Some process schemes allow the cut pattern to land on the spacer, to be confined by the spacer. As a result, an overlay budget and CD variation budget of the cut pattern is about half of the spacer width. In some occasions, only one feature at a minimum pitch will be cut. Therefore, a very small cut feature is needed. The pattern fidelity of such a small feature is often not desirable, and the total budget for overlay and CD variation is insufficient.
Accordingly, what is needed is a method to extend the overlay budget and CD variation budget of cut patterns.